Science is the systematic study of the natural world. It helps us
understand phenomena through observation, questioning, experimentation,
and evidence-based conclusions.
It is often called the art of asking questions because
scientific progress begins by noticing something interesting or unexplained,
then trying to explain it logically.
Branches of Science:
Biology: Study of living organisms, their structure,
functions, and interactions. Includes studying cell systems, tissues,
organs, and organ systems.
Chemistry: Study of substances, elements, compounds,
and their changes during reactions.
Physics: Study of energy, motion, forces, light, heat,
and sound.
Earth & Space Science: Study of the Earth, its
atmosphere, geology, oceans, planets, stars, and the universe.
Why Science is important:
Helps us understand natural events and solve problems.
Supports technology, medicine, and innovation.
Encourages curiosity and critical thinking.
Science is a way of thinking, not just memorizing facts.
Living vs Non-living:
Living things grow, reproduce, respond to the environment, and have cells.
Non-living things do not grow or reproduce and lack cells.
Cells are the basic units of life — forming tissues, organs, and systems.
1.2 Scientific Inquiry
Scientific inquiry is the process of asking questions and performing
investigations to gather evidence and reach conclusions.
Steps of Scientific Inquiry:
Observing carefully using senses or instruments.
Asking questions about what is observed.
Forming hypotheses — possible explanations.
Predicting outcomes based on hypotheses.
Designing and conducting experiments.
Collecting and analyzing data.
Drawing conclusions based on evidence.
Communicating results to others.
Key Concepts:
Observations: What you notice or measure.
Inferences: Logical explanations based on observations.
Predictions: Statements about what may happen in the future.
Variables in Experiments:
Independent variable: The factor intentionally changed.
Dependent variable: The factor measured to see the effect.
Controlled variables: All factors kept constant to ensure a fair test.
A fair test changes only one variable at a time while keeping everything else the same.
Importance of Repeated Trials:
Helps reduce errors and improve reliability.
Ensures results are consistent and not due to chance.
1.3 Laboratory Skills and Safety
Laboratory work is a key part of science learning. It allows scientists
to test ideas and gather evidence in a controlled environment.
Nutrients absorbed in small intestine; water absorbed in large intestine.
Waste removed through rectum and anus.
All body systems work together — for example, muscles need oxygen from the circulatory system, which comes from the respiratory system, and energy comes from nutrients absorbed via the digestive system.
UNIT 3: Matter and Materials
3.1 States of Matter
Matter exists in different states depending on the arrangement and movement of particles.
Solids: Particles are closely packed in a fixed structure; vibrate in place. Fixed shape and volume; incompressible.
Liquids: Particles are close but can move past each other; takes the shape of the container but has fixed volume; slightly compressible.
Gases: Particles are far apart, moving freely at high speed; no fixed shape or volume; highly compressible.
Additional Concepts:
Plasma: Ionised gas with free electrons; conducts electricity, found in stars.
Bose-Einstein Condensates: Ultra-cold state where particles act as a single quantum entity.
Particle theory explains density, diffusion, and pressure in different states.
Particle arrangement and motion explain why ice floats on water (less dense) and why gases expand to fill containers.
3.2 Changes in State
Matter can change states when energy (usually heat) is added or removed.
Melting: Solid → Liquid. Particles gain kinetic energy to break rigid bonds.
Freezing: Liquid → Solid. Particles lose energy and settle into fixed positions.
Evaporation: Liquid → Gas. Particles at surface escape into gas phase.
Boiling: Liquid → Gas throughout liquid at boiling point.
Condensation: Gas → Liquid. Particles lose energy and form bonds.
Sublimation: Solid → Gas directly (e.g., dry ice).
Deposition: Gas → Solid directly (e.g., frost formation).
Energy Changes: Endothermic: energy absorbed (melting, evaporation); Exothermic: energy released (freezing, condensation).
Heating curves show plateau regions where temperature remains constant as energy is used to break bonds, not raise temperature.
3.3 Physical and Chemical Changes
Changes in matter can be physical (no new substance) or chemical (new substances formed).
Physical Changes: Changes in state, shape, or appearance without changing composition. Often reversible. Examples: melting ice, dissolving sugar, breaking glass.
Chemical Changes: Changes that form new substances with different properties. Usually irreversible. Examples: burning wood, rusting iron, baking a cake.
Indicators of chemical change:
Gas production (bubbles or fizzing)
Color change
Temperature change (exothermic or endothermic)
Formation of precipitate
Light or sound produced
Observing carefully and recording changes helps distinguish physical from chemical changes in experiments.
3.4 Materials and Their Properties
Materials have characteristic properties that determine their use in everyday life and technology.
Hardness: Resistance to scratching or indentation (e.g., diamond vs chalk).
Flexibility: Ability to bend without breaking (e.g., rubber, metals like copper).
Transparency: How much light passes through (glass vs wood).
Conductivity: Thermal and electrical conductivity; metals are good conductors, plastics are insulators.
Density: Mass per unit volume; important in material selection.
Solubility: How well substances dissolve in solvents (salt in water vs sand).
Magnetism: Attraction to magnetic materials (iron, nickel).
Elasticity: Ability to return to original shape after stretching (e.g., spring steel, rubber bands).
Engineers and scientists select materials based on a combination of physical, chemical, and mechanical properties.
UNIT 4: Forces and Energy
4.1 Forces
Forces are pushes or pulls that can change the motion, direction, or shape of objects.
Types of Forces:
Contact forces: Forces where objects physically touch.
Friction – resists motion between surfaces.
Tension – force in ropes, strings, or cables.
Normal force – supports objects on surfaces.
Applied force – direct push or pull.
Air resistance – friction of air against moving objects.
Non-contact forces: Forces acting at a distance.
Gravitational force – attraction between masses.
Magnetic force – attraction/repulsion between magnetic materials or poles.
Electrostatic force – attraction/repulsion between charged objects.
Charge in Electrostatics:
Positive charge (+): Often carried by protons; repels other positive charges.
Negative charge (−): Carried by electrons; repels other negative charges.
Opposite charges attract; like charges repel.
Charge is conserved: cannot be created or destroyed, only transferred.
Forces are vector quantities – they have both magnitude and direction. They can be represented using arrows in diagrams.
4.2 Effects of Forces
Change the speed of an object (acceleration or deceleration).
Change the direction of motion (turning or curving).
Change the shape of an object (compression, stretching, bending).
Maintain equilibrium when balanced (net force = 0).
Newton’s Laws of Motion:
1st law (Inertia): Objects stay at rest or in motion unless acted on by an external force.
2nd law: Force = Mass × Acceleration (F = ma).
3rd law: For every action, there is an equal and opposite reaction.
4.3 Energy
Energy is the ability to do work or cause change. It exists in multiple forms:
Kinetic energy: Energy of moving objects (depends on mass and velocity).
Potential energy: Stored energy due to position or condition (e.g., stretched spring, elevated object).
Thermal energy: Energy due to particle motion (heat).
Electrical energy: Energy from moving electrons in a circuit.
Light energy: Energy carried by electromagnetic waves.
Sound energy: Vibrations traveling through a medium.
Chemical energy: Stored in chemical bonds (food, fuel).
Nuclear energy: Stored in atomic nuclei (fusion and fission).
Electricity and Circuits:
Electric current = flow of electrons through a conductor.
Voltage = energy per unit charge; measured in volts (V).
Resistance = opposition to current flow; measured in ohms (Ω).
Resistors are components used to limit current, divide voltage, or protect devices.
Ohm’s Law: V = I × R (Voltage = Current × Resistance).
Series circuits: current is the same; voltages add.
Parallel circuits: voltage is the same; currents add.
Conductors allow electrons to flow easily (metals), while insulators resist flow (rubber, plastic). Resistors are deliberate obstacles in circuits to control current.
4.4 Energy Transfer and Forces in Action
Energy can be transferred from one form to another and can do work through forces.
Mechanical work: Force × Distance in the direction of force.
Gravitational potential → kinetic (e.g., rolling ball).
Forces can accelerate, decelerate, change direction, or deform objects.
All forces interact; combined forces can be analyzed using vector diagrams.
Understanding forces and energy together explains everyday phenomena: why brakes stop a car, why objects fall, and how electricity powers devices.
UNIT 5: Environment and Sustainability
5.1 Ecosystems
An ecosystem is a community of living organisms interacting with each other and their physical environment.
Producers (Autotrophs): Make their own food using sunlight (photosynthesis) or chemical energy (chemosynthesis). Examples: plants, algae, some bacteria.
Consumers (Heterotrophs): Depend on other organisms for food.
Primary consumers – herbivores (eat producers)
Secondary consumers – carnivores or omnivores (eat herbivores)
Tertiary consumers – apex predators
Decomposers: Break down dead plants, animals, and waste, recycling nutrients into the soil. Examples: fungi, bacteria, detritivores.
Abiotic components: Non-living parts like sunlight, water, air, temperature, and soil.
Interactions in ecosystems: Symbiosis, predation, competition, mutualism, commensalism, parasitism.
Healthy ecosystems maintain balance between producers, consumers, and decomposers, cycling energy and matter efficiently.
5.2 Food Chains and Food Webs
Energy flows through ecosystems via food chains and food webs.
Food chain: Linear flow of energy from producers → primary consumers → secondary consumers → tertiary consumers.
Food web: Interconnected food chains showing multiple feeding relationships in an ecosystem.
Energy transfer: Only ~10% of energy is passed to the next level; the rest is lost as heat (Second Law of Thermodynamics).
Trophic levels: Each step in a food chain (producer, primary, secondary, tertiary consumer).